In macOS High Sierra, Apple introduced support for external GPUs for the first time, made possible through Metal 2. Developers were able to begin optimizing their apps for eGPUs when High Sierra was released, and in the 10.13. 4 update, released in March, official eGPU support was implemented.

Does macOS Sierra have Metal?

Metal has been available since June 2, 2014 on iOS devices powered by Apple A7 or later, and since June 8, 2015 on Macs (2012 models or later) running OS X El Capitan. On June 5, 2017 at WWDC, Apple announced the second version of Metal, to be supported by macOS High Sierra, iOS 11 and tvOS 11.

What does macOS High Sierra support?

These Mac models are compatible with macOS High Sierra: MacBook (Late 2009 or newer) MacBook Pro (Mid 2010 or newer) MacBook Air (Late 2010 or newer)